This invention relates to a monolithically integrated, transistor bridge circuit and a method for the manufacture thereof.
More particularly, the invention relates to a bridge circuit made up of power transistors operated at a high voltage which may exceed 250 volts, although the description which follows will make reference to an application of this kind merely for convenience of illustration.
As is known, bridge circuits are widely used for a large number of applications on account of their ability to equalize currents being supplied to an electric load.
For such specific applications, integrated circuits incorporating bipolar transistors or field-effect transistors in a half-bridge configuration have been provided in the past. A circuit of that type is described, for example, in Italian Patent No. IT 1204522 of SGS-Thomson, which is hereby incorporated by reference.
Another known technical solution is described in European Patent Application No. 91830513.7 (which is hereby incorporated by reference), which relates to an integrated bridge circuit of the type designed to optimize power losses. The approach of this application has proved advantageous by virtue of its high conversion efficiency and its ability to operate on high currents, but does not provide for integration of all the power components on a single chip.
The present invention advantageously provides a transistor bridge circuit which has such structural and functional features as to enable monolithic integration of high-voltage elements, while overcoming the current limitations of prior art embodiments. This is accomplished by combining high current-carrying IGBT devices, in combination with junction bipolar devices, into the integrated circuit. Preferably the IGBT devices are connected between output nodes and a positive power supply connection, and the junction bipolar devices are connected between the output nodes and ground.
The present invention also advantageously provides a bridge circuit which can be readily manufactured, and a process for manufacturing it.